A new feathered and four-winged dinosaur

Now that my book’s turned in, I have a chance to catch up on the stack of biology papers I’ve had to neglect. I hope to be posting more about them in the next couple of weeks, but be aware that the Dreaded Edits to the book will come back when I’ve returned from Poland, and that, along with dealing with references, formatting, and the like, will probably take a few months of work.

But, in the meantime, there’s a a cool new paper in Nature Communicationsby Gang Han et al. (reference and download below) describing the discovery of a four-winged dinosaur in fossil deposits from the Early Cretaceous (about 125 million years ago) in China. As you know, most of the good feathered dino fossils come from China, for that country has marvelous deposits of silt that produced good preservation of feathers.

Your first question will be this: could it fly? The answer is “we don’t know.” (That’s often true of these feathered dinos, which could have been gliders rather than fliers). And this is not the first “four-winged” dinosaur. What’s notable about it is its size (BIG) and its highly feathered tail.

Also, do remember that four-winged dinosaurs didn’t really have four wings: they usually had front appendages that were winglike and highly feathered, but legs that were less feathered. They also had bony tails, like all dinos, which were also feathered.

None of them, as far as I remember, can definitely be said to have flown: they could have been gliders, and could have glided to escape predators, to move from tree to tree, to glide down on prey, or all of the above. The first one discovered was Microraptor gui, which looked something like this:

That out of the way, the new species is named Changyuraptor yangi. “Changyu” means “long feather” in Chinese, “raptor” refers to the fact that it was a predator—see teeth below—and the species name honors Professor Yang Yudong, who apparently provided the finances to purchase the fossil.

It’s a theropod dinosaur, the ancestors of birds, and falls in the family Dromaeosauridae, a group of bipeda (walked on its hind legs) and predatory theropods. The specimen, shown below, is remarkably well preserved, at least below the neck. But there are parts of the head and the teeth remaining. In the fossil below you can make out the feather impressions along the neck, the forelimbs, the hindlimbs, and along the long, bony tail (remember, this was a dinosaur, not a tailless bird!). The length of the black line at the bottom is 10 cm (about 4 inches), so the thing was about 132 cm long from the tip of the beak to the tip of the tail. That’s 51 inches, or about 4.25 feet, so this is a large specimen!

Here’s a reconstruction of the skeleton with the feather impressions shaded in. The section at the bottom is a bit of the femur impression, showing the “LAG,” or “line of arrested growth,” from which the authors conclude that this was an adult specimen, at least five years old.

Some details of the skeleton: a. tail vertebrae, b. some of its teeth (notice they’re sharp; these things, like other feathered dinos, these were predators; c. furcula (“wishbone”) and shoulder girdle, and d. a foot. The scale bar is 1 cm.

Here are impressions of the feathers (see caption below the photo for details). The authors conclude that this species had the longest feathers of any known “non-avian dinosaur” (I’m checking with the experts to see exactly what distinguishes a “non-avian dinosaur” from either an “avian dinosaur” or a “bird”). The tail feathers were up to 30 cm long—almost a foot. That exceeds by several inches the longest known feathers in similar dinosaurs, but of course this was one of the largest flying/gliding dinosaurs.

Figure 4 | Details of the plumage of HG B016 as preserved on slab A. (a) Graduated distal rectrices, (b) feathers surrounding the shoulder girdle, (c) portion of the left hindwing and (d) portion of the right hindwing. Scale bar, 2 cm.

As I said, this is a well-feathered dino, but the authors still can’t conclude that it flew. That, I suppose would depend both on finding better feather impressions (flying feathers are asymmetrical) and knowing something about the musculature, which isn’t preserved. This is above my pay grade, but I suppose it’s almost impossible to conclude from a fossil of this type whether it flew, even if the feathers were asymmetrical. But at the very least it glided, and probably well.

The authors make a big deal about the feathered tail, wondering what function it served for a glider. They conclude it controlled “pitch”, or the ability of the animal to control its movement from “head up” to “head down”. That is, imagine the bird with wings extended and a rod stuck through the wings from one side to the other. You could then move the body up and down like a seesaw (head goes up, tail goes down) around this axis (see here for a demonstration). That would enable the bird to make a good landing if it were coming in from above. But here, I’ll let you read the conclusion, since it’s not too technical (my emphasis):

Combined with the possibility of passive flexion of the distal tail to take on both positive and negative angles of attack, this caudally oriented combination of lift and drag may have acted to reduce descent speed while simultaneously providing passive stability in the pitching axis, which could be critical to a safe landing or precise attack on prey. Such pitch stabilization could be particularly important for larger microraptorines (since they would tend to fly and/or descend more rapidly than small individuals), and this effect explains why the tail fan is exceptionally long in HG B016 [the specimen]. A pitch control function also explains why the feathered tails of microraptorines are proportionally much longer than in other maniraptorans, as this would extend the moment arm for pitch control by the tail. The discovery of HG B016 thus supports the hypothesis that the extended tail and long, fanned retrices of microraptorines played a key aerodynamic role, allowing them to retain aerial and/or semi-aerial competency at relatively large body sizes. The remarkably long-feathered tail Changyuraptor yangi helps us understand how such low-aspect-ratio tails operated as pitch control structures that reduced descent speed during landing.

If I had a time machine, and could go back to, say, five periods of evolutionary history, one of them would be this time, so we could see exactly what these beasts looked like and whether they flew. (A thought experiment I often think about is this; if you’re given a machine to go back to one time in evolutionary history, and were given only a notepad and pen, where and when would you go to answer the most pressing and difficult questions of evolution?)

With regards to your thought experiment, I’ve long thought that 100,000 years ago would have be an interesting time. If I recall correctly, there are believed to have been about six different human species in existence. That would have been fascinating.

If not that then the Devonian, to see our fishy ancestors crawling out of the sea. Although when were those giant armoured fish around? Oooh, so many times to choose from!

A thought experiment I often think about is this; if you’re given a machine to go back to one time in evolutionary history, and were given only a notepad and pen, where and when would you go to answer the most pressing and difficult questions of evolution?

I don’t get the notepad and pen, why not taking a sample back with?

I guess I would like to go right after life started, to get a sample telling us what geophysical system spawned life, and what its original metabolism was. Failing that: the UCA period, to get a better handle on its genome.

Paper and pen would be the Australopithecus/Homo transition, to get a tighter constraint on the Homo root.

We already had that world–the superintelligent cats sat around thinking ‘hey wouldn’t it be great to lie around all day getting fed and petted?’ so they invented a time machine and prevented the handshake with Lucy so it never happened. *Phew*

This is fascinating. I’m really interested in the evolution of birds and every discovery seems cooler than the last. I’m still reeling from the Microraptor fossil with bird bones in its stomach, now I read this. Wow!

Even the canonical early bird, Archaeopteryx, appears to have had feathered legs like the other ‘four winged’ dinosaurs. This is according to examination of a fossil that shows the leg feathers. It is described here.

It’s controversial. The study you recall is Xu et al. (2011), which placed Archaeopteryx at the base of the group closest to birds (Deinonychosauria, including Velociraptor and this new specimen). Lee and Worthy (2011) analyzed the same data a different way and found Archaeopteryx to be a bird, but their method isn’t used by any other dinosaur workers, produced some weird results and may not be useful for these kinds of analyses. Most more recent analyses (e.g. Turner et al., 2012; Foth et al., 2014) find Archaeopteryx to be a bird, but honestly it’s so similar to the common ancestor of deinonychosaurs and birds that neither placement is much more strongly supported.

As for the question of what makes a non-avian dinosaur, in this case the authors are using Aves in the sense of Archaeopteryx and species closer to living birds. So every dinosaur less closely related to birds than Archaeopteryx is a nonavian dinosaur. If you meant which physical features distinguish Aves, this depends on which analysis you use. The Changyuraptor analysis is based on Turner et al.’s, which found 16 characters diagnose this group (listed on page 115 of Turner et al. under Avialae).

That question did cross my mind too. I suspect it’s not a can of creationist-agitating worms that people really feel a need to open. (Mickey Mortimer, upthread, seems to be much more up to scratch on this stuff than I am, so he may have a much more valuable 0.20€ coin to throw into this fountain.)
You could as-well describe it as a 4-winged and 1-ruddered bird(-ish).

I want to go back to the High Plains during the mid-Oligocene (25 million years ago) to see the Nimravids (sabertoothed animals similar to cats, but in their own extinct family) and Proailurus (a possible Felid ancestor).
I’ll need a “rite-in-the-rain” notebook, my Staedtler Lumograph drawing pencils, and some way of outrunning giant hyaenas and Entelodonts (giant carnivorous warthogs).

I’m thinking the late Proterzoic, almost a billion years ago, when vertebrate and invertebrate lineages split. Right before the Cambrian explosion. We have such a poor fossil record from that time, and we know there had to have been a great deal of diversity, and everything would have been radically different from our common experience of terrestrial life…and yet, we evolved from that.

Much before, and your Mark I Eyeball isn’t going to be up to the task of observing the interesting action. Much after and things start to settle down.

A thought experiment I often think about is this; if you’re given a machine to go back to one time in evolutionary history, and were given only a notepad and pen, where and when would you go to answer the most pressing and difficult questions of evolution?

I’d break the rules, dump the pencil and pad, and bring back a polythene bag of trilobites. And if I came back to a world run by super-intelligent shades of the colour blue, I’d probably be happy with that.
I’d still be deeply tempted to go and retrieve a clutch of Triceratops eggs too.

I want to go back to watch Neanderthals living in Europe, and then back to watch Homo erectus, to see if they had language (I’m betting yes). I’d also like to go to the late Precambrian to look at early metazoans. If I could bring something back I’d go and get a trilobite or three.